Refrigerant flow control for maintaining minimum head



April 25, 1967 H. W. KIRTLAND ETAL REFRIGERANT FLOW CONTROL FORMAINTAINING MINIMUM HEAD Filed Feb. 16, 1966 FIG. 2

FIG. I

INVENTORS. W. KIRTLAND. R. CHECK HOWARD B DONALD ATTORNEY.

United States Patent 3,315,482 REFRIGERANT FLOW CONTROL FOR MAIN-TAINING MINIMUM HEAD Howard W. Kirtland, East Syracuse, N.Y., and DonaldR. Check, Minneapolis, Minn., assignors to Carrier Corporation,Syracuse, N.Y., a corporation of Delaware Filed Feb. 16, 1966, Ser. No.527,877 3 Claims. (Cl. 62-115) This invention relates broadly to arefrigeration machine. More particularly, this invention relates to thecontrol of refrigerant flow in a refrigeration machine. Still moreparticularly, this invention relates to a liquid refrigerant meteringdevice particularly equipped to provide a rapid refrigerant pressureincrease in the high pressure side of a refrigeration machine at startup and to maintain minimum pressure therein under abnormal conditions.

In high tonnage refrigeration machines, a compressor is arranged toextract gaseous refrigerant from an evaporator, compress therefrigerant, and pump it to a condenser where it is cooled andcondensed. In communication with the condenser, there is normallyprovided a receiver for collecting liquid refrigerant formed in thecondenser prior to its passage to the evaporator. The receiver usuallycontains refrigerant both in the liquid and gaseous phases. In someinstances, a portion of the liquid refrigerant is utilized to cool themotor driving the refrigerant compressor. To insure suflicientrefrigerant flow to the motor being cooled, a minimum refrigerantpressure differential in the machine is required.

To maintain a liquid seal in the receiver, a metering device is employedto regulate refrigerant flow from the condenser or receiver to theevaporator. Under normal operating conditions, the level of the liquidrefrigerant collected in the receiver is a function of the pressuredifference between the high pressure side of the machine and the lowpressure side of the machine and the load on the machine, it beingunderstood the condenser is disposed in the high pressure side and theevaporator in the low pressure side of the machine. Refrigerant flowfrom the condenser to the evaporator occurs in an amount related to theloading on the machine and automatic controls such .as suction guidevanes are provided for the purpose of maintaining flow ratescorresponding to machine loading. Float operated valve assemblies areprovided to pass a predetermined amount of refrigerant in accordancewith the level of liquid refrigerant collected to maintain a liquid sealin the receiver.

The liquid from the receiver is passed through the metering device tothe evaporator. The evaporator contains a multiplicity of tubes usuallyreferred to as a tube bundle through which the medium to be cooled ispassed in heat transfer relation with the refrigerant in the evaporator.

Under normal operating conditions, the pressure in the refrigerationmachine is sufiicient to force the desired quantity of liquidrefrigerant from the receiver or condenser to the refrigerant compressormotor to provide proper cooling thereof. However, at start up or underabnormal operating conditions, the pressure difference between thereceiver or condenser and the motor casing may be insufficient to forcethe required liquid refrigerant to the compressor motor.

The chief object of this invention is to provide a refrigerant controldevice which will provide for rapid pressure increase in the highpressure side of the machine when it is started and maintain a minimumpressure difference therein under abnormal operating conditions. It isan additional object of this invention to provide a refrigerant controldevice which will maintain a liquid seal in the receiver under normaloperating conditions. Another object of this invention is to provide animproved method for controlling refrigerant flow in a refrigerationmachine between the high pressure and the low pressure sides thereof.

The objects of this invention are attained by providing a cylinderhaving one end in communication with the interior of the receiver. Acontrol line is provided between the other end of the cylinder and theevaporator. A piston disposed within the cylinder is operably connectedto a refrigerant metering float valve assembly through a push rod. Aspring in the cylinder biases the piston and push rod against therefrigerant metering float valve assembly to maintain the valve closeduntil a sulficient pressure differential is built up between theevapor-ator and condenser or receiver to overcome the spring force andmove the piston with the push rod attached, out of engagement with thefloat valve.

Other objects and features of this invention will be apparent uponconsideration of the ensuing specification and drawing in which:

FIGURE 1 is an elevational view partially in section of a portion of arefrigeration machine incorporating the preferred embodiment of therefrigerant float control mechanism forming the subject of thisinvention.

FIGURE 2 is a fragmentary view, partly in section, of the receiverportion of the refrigeration machine illustrating the float valve andregulating mechanism.

Referring more particularly to the drawing, there is shown a centrifugalrefrigeration machine 1 for cooling a relatively large quantity of Waterfor flow in a closed circuit forming a part of an air conditioningplant. The machine 1, having motor driven refrigerant compressor 2,includes shell 3 for housing the heat transfer units associated with themachine. The shell 3 has a partition 4 therein for separating the highpressure condenser section 5 from the low pressure evaporator section 6.Tube bundle 7 in evaporator section 6 is provided for passing the waterto be chilled therethrough. Lines 8' and 8" provide a path of flow for aportion of the liquid refrigerant formed in the condenser through themotor compressor to cool the motor.

Refrigerant receiver or float box 8 is provided for receiving gaseousand liquid refrigerant from the condenser through an opening 9communicating therewith. Float valve assembly 10 in float box 8 isprovided for metering refrigerant from the float box to the evaporatorsection 6 through passage-way 9'. The float valve assembly 10 com-prisesfloat ball 11, float arm 12, and throttle plates 13. The float valveassembly is pivoted on pin 14 mounted in the sides of an opening 14' inthe floor of the box. A cylinder 15 is provided in the float box havingone end 15' thereof in communication with the interior of float box 8and the other end 15" in communication with evaporator 6 through controlline 16. A piston 17 in cylinder 15 is biased toward the end 15 ofcylinder 15 by spring 18. Push rod 19 solidly aflixed to piston 17 isprovided to hold float valve assembly 10 closed to prevent communicationbetween the high pressure side of the machine and the low pressure sideof the machine when the piston 17 is displaced toward the end 15' ofcylinder 15.

Considering the operation of this refrigerant metering deviceundernormal operating conditions, the pressure differential between thecondenser and evaporator will be suflicient to overcome the force ofspring 18 and displace piston 17 toward the end of cylinder 15 incommunication with the evaporator. Push rod 19, therefore, will notinterfere with the normal operation of float valve assembly 10. As such,float valve assembly 10 will maintain a constant liquid refrigerantlevel in float box 8.

At start up or under abnormal operating conditions when the pressurebetween the condenser and evaporator is at or below the desired minimumdifference, spring 18 will force piston 17 with push rod 19 attachedagainst float valve a-rm'12 to maintain valve closed until the pressuredifferential between the evaporator and condenser exceeds the desiredminimum.

This will insure a pressure differential under most operating conditionssuflicient to provide liquid refrigerant flow to the refrigerantcompressor motor so that the motor is properly cooled.

" While we have described a preferred embodiment of our invention, it isto be understood that the invention is not limited thereto but may beotherwise embodied 7 within the scope of the following claims. -Weclaim:

1. A refrigerant metering device disposed in the high pressure side of arefrigeration machine for controlling flow of refrigerant to the lowpressure side of the machine comprising:

a float valve assembly operable in response to liquid refrigerant levelin the high pressure side of the machine to pass refrigerant to theevaporator, and

actuator means operable in response to a predetermined refrigerantpressure difference between the high pressure and low pressure sides ofthe machine to maintain said float valve closed irrespective ofrefrigerant level in the high pressure side of the machine.

2. A refrigerant metering device according to claim 1 wherein saidactuator means comprises:

a pneumatic cylinder in the high pressure side of the machine having oneend in communication with the high pressure side of the machine and theother end in communication with the evaporator of the refrigerationmachine,

a piston slidably disposed in said cylinder,

a spring biasing said piston away from the end of the cylinder incommunication with the evaporator, a push rod solidly aflixed to saidpiston between the float valve and said piston to hold said float valveclosed irrespective of the refrigerant level in the high pressure sideof the machine when said piston is displaced in a directionaway from theend of the cylinder in communication with the evaporator.

3. The method of controlling refrigerant flow in a refrigeration machinewhich consists in the steps of regulating a passage of liquidrefrigerant from the high pressure side of the machine to the lowpressure side of the machine by mechanism operable in response to thelevel of liquid refrigerant collected in the high pressure side of themachine, and

overriding the action of said mechanism when the pressure differentialbetween the high pressure and low pressure sides of the machine is belowa desired minimum to hold said mechanism closed until the de-' siredminimum pressure diflerential is attained.

References Cited by the Examiner UNITED STATES PATENTS 2,589,859 3/1952Phillips 62174 2,7l5,317 8/1955 Rhodes 62-149. 2,871,673 2/1959 Richardset al 62509 X 2,921,446 1/1960 Zulinke 62-1l7 3,248,895 5/1966 Mauer62174 X LLOYD L. KING, Primary Examiner.

3. THE METHOD OF CONTROLLING REFRIGERANT FLOW IN A REFRIGERATION MACHINEWHICH CONSISTS IN THE STEPS OF REGULATING A PASSAGE OF LIQUIDREFRIGERANT FROM THE HIGH PRESSURE SIDE OF THE MACHINE TO THE LOWPRESSURE SIDE OF THE MACHINE BY MECHANISM OPERABLE IN RESPONSE TO THELEVEL OF LIQUID REFRIGERANT COLLECTED IN THE HIGH PRESSURE SIDE OF THEMACHINE, AND OVERRIDING THE ACTION OF SAID MECHANISM WHEN THE PRESSUREDIFFERENTIAL BETWEEN THE HIGH PRESSURE AND LOW PRESSURE SIDES OF THEMACHINE IS BELOW A DESIRED MINIMUM TO HOLD SAID MECHANISM CLOSED UNTILTHE DESIRED MINIMUM PRESSURE DIFFERENTIAL IS ATTAINED.